Fluorescent liquid toner and method of printing using same

ABSTRACT

Charged toner particles for use in electrostatic imaging, comprising: a toner polymer; and at least one particulate fluorescent material, wherein the toner particles are formed with fibrous extensions.

RELATED APPLICATIONS

The present application is a U.S. national application of PCTApplication No. PCT/IL00/00277, filed 17 May 2000.

FIELD OF THE INVENTION

The present invention is related to the field of electrostatographicprinting and especially to the field of printing using fluorescenttoner.

BACKGROUND OF THE INVENTION

Modern liquid toner electrostatic imaging began with the invention of anew class of toners referred to herein as ElectroInk® (which is atrademark of Indigo, N.V. of The Netherlands). This toner ischaracterized by its comprising toner particles dispersed in a carrierliquid, where the toner particles are comprised of a core of a polymerwith fibrous extensions extending from the core. When the tonerparticles are dispersed in the carrier liquid in a low concentration,the particles remain separate. When the toner develops an electrostaticimage the concentration of toner particles increases and the fibrousextensions interlock. A large number of patents and patent applicationsare directed toward this type of toner and charge directors which arecomprised in it. These include: U.S. Pat. Nos. 4,794,651; 4,842,974;5,047,306; 5,407,307; 5,192,638; 5,208,130; 5,225,306; 5,264,312;5,266,435; 5,286,593; 5,300,390; 5,346,796; 5,407,771; 5,554;476;5,655,194; 5,792,584 and 5,5923,929 and PCT Patent publicationWO/92/17823, the disclosures of all of which are incorporated herein byreference.

It has been discovered that this type of toner allows for high qualityoffset printing at high speed. However, this type of printing isdescribed inter alia in patents and patent application numbers4,678,317; 4,860,924; 4,980,259; 4,985,732; 5,028,964; 5,034,778;5,047;808; 5,078,504; 5,117,263; 5,148,222; 5,157,238; 5,166,734;5,208,130; 5,231,454; 5,255,058; 5,266,435; 5,268,687; 5,270,776;5,276,492; 5,278,615; 5,280,326; 5,286,948; 5,289,238; 5,315,321;5,335,054; 5,337,131; 5,376,491; 5,380,611; 5,426,491; 5,436,706;5,497,222; 5,508,790; 5,527,652; 5,552,875; 5,555,185; 5,557,376;5,558,970; 5,570,193; the disclosures of which are incorporated hereinby reference. Systems incorporating various ones of these patents aresold under the names E-Print 1000®, Ominius®, Turbostream™ andCardpress™.

In general, ElectroInk comprises a polymer or polymers (usuallypigmented) which solvate the carrier liquid at some temperature aboveroom temperature (and preferably above normal storage temperatures of30-40° C.) and do not solvate the carrier liquid or dissolve substantialamounts of it below that temperature. Above the solvation temperaturethe polymer adsorbs the carrier liquid and is plasticized and softenedby it. At elevated temperatures the toner material is thus soft enoughto bond with a paper substrate. In practice, the temperature andpressure at which transfer to paper is made are controlled so that thetransfer is complete, the transferred toner is fixed to the paper andthe image is not squashed.

U.S. Pat. No. 5,908,729, the disclosure of which is incorporated byreference, describes, inter alia, a fluorescent toner, i.e., chargedtoner particles dispersed in a carrier liquid, where the toner particlesare colored with a particulate fluorescent pigment. However, thedisclosed toner is not of the type described above. Rather, the pigmentis mixed with a low density polyethylene in a planetary mixer. The tonerthus formed is not fibrous, but rather is in the form of the particulatematerial coated with the polyethylene.

SUMMARY OF THE INVENTION

An aspect of some embodiments of the invention is concerned withfluorescent toner having fibrous extensions. In some embodiments of theinvention, the fluorescence is provided by particulate fluorescentpigment.

An aspect of some embodiments of the invention is concerned with methodsof manufacture of fluorescent toner. In some embodiments of theinvention, the toner is manufactured by grinding a mixture ofthermoplastic polymer material, fluorescent pigment and carrier liquidto form the toner particles. The toner particles will then generallyhave fibrous extensions.

An aspect of some embodiments of the invention is concerned with tonerparticles comprising a fluorescent pigment material and anothercolorant. The other colorant may be a pigment, or a dye. The othercolorant may have a relatively strong color and a weak or nofluorescence. The fluorescent pigment may have strong fluorescence andrelatively weal, “normal” color. In addition, the fluorescent pigmentmay have a different hue from other pigment.

One type of useful pigment is particles of a fluorescent dye dissolvedin a rigid solid polymer matrix. This type of pigment is generallyoptimized for high fluorescence, by providing an optimum dilution of thedye and an environment that has relatively low quenching of thefluorescence, while environmentally protecting the dye. Examples of suchpolymer matrices are formaldehyde resins. However, other resins,including thermosetting resins are known for producing such pigments.

Generally, the pigments have a size of 2-4 micrometers, although largerand smaller sized particles can be used. This is as large as, or largerthan ElectroInk produced with normal pigment, which is much smaller thanthe fluorescent pigments. Toner particles utilizing the fluorescenttoner have a particle size, generally depending on the size of thepigment, of 3 to 10 micrometers, more generally between 5 and 9micrometers. This size may vary to an even greater extent, especiallywhen very large or small pigments are used.

There is also provided, in accordance with some embodiments of theinvention, Charged toner particles for use in electrostatic imaging,comprising: a toner polymer; and at least one particulate fluorescentmaterial, wherein the toner particles are formed with fibrousextensions.

In an embodiment of the invention, the particles include a pigmentadditional to the at least one particulate fluorescent material.

There is further provided, in accordance with some embodiments of theinvention, charged toner particles for use in electrostatic imaging,comprising: a toner polymer, at least one particulate fluorescentmaterial; and a pigment, additional to the particulate fluorescentmaterial.

In exemplary embodiments of the invention, the additional pigment is anorganic pigment. In some embodiments the additional pigment isfluorescent; in others it is not fluorescent. In some embodiments of theinvention, the fluorescent color of the at least one particulatefluorescent material is different from that of the pigment. In exemplaryembodiments of the invention, the at least one particulate material andthe pigment is greater than about 30% by weight of the total dry solidsof the toner particle. In others it is greater than about 40% or 45% byweight of the total dry solids of the toner particle.

In exemplary embodiments of the invention, the particulate fluorescentmaterial comprises an encapsulated dye material. In some embodiments thedye material is encapsulated in an encapsulating polymer, such as athermoplastic polymer, or a thermosetting polymer.

In some exemplary embodiments of the invention, the particulatefluorescent particulate material is in the form of pigment particleshaving a size greater than about 2, 3, or 4 micrometers.

In some exemplary embodiments of the invention, the toner particle sizeis greater than about 3 or 5 micrometers. In some exemplary embodiments,the toner particle size is smaller than about 9 or 10 micrometers.

In exemplary embodiments of the invention, the particulate fluorescentmaterial comprises more than 40% or 50% of the non-volatile solidsportion of the particle.

In some exemplary embodiments of the invention, the toner polymercomprises an ethylene methacrylic acid copolymer.

There is further provided, in accordance with some embodiments of theinvention, a liquid toner, comprising: a carrier liquid; and chargedtoner particles according to any of the preceding claims dispersed inthe carrier liquid.

In exemplary embodiments of the invention, the carrier liquid issubstantially non-conducting.

In exemplary embodiments of the invention, the liquid toner includes acharge director for aiding in the charging of the toner particles.

There is further provided, in accordance with some embodiments of theinvention, a method of producing a liquid toner comprising:

-   -   mixing a toner polymer, a carrier liquid and a particulate        fluorescent material;    -   grinding the mixture until toner particles are produced.

In some embodiments, mixing comprises mixing a pigment additional to theat least one particulate fluorescent material with the other materials.

There is further provided, in accordance with some embodiments of theinvention, a method of producing a liquid toner comprising:

-   -   mixing a toner polymer, a carrier liquid, a particulate        fluorescent material and a pigment in addition to the        particulate fluorescent material;    -   grinding the mixture until toner particles are produced.

In some embodiments of the invention, the additional pigment is anorganic pigment. In some embodiments, the additional pigment isfluorescent. In others, the pigment is not fluorescent. In someembodiments of the invention, the fluorescent color of the at least oneparticulate fluorescent is different from that of the additionalpigment.

In exemplary embodiments of the invention, the at least one particulatematerial and the pigment is greater than about 30, 40 or 45% by weightof the total dry solids of the mixture.

In exemplary embodiments particulate fluorescent material comprises anencapsulated dye material. In some embodiments the dye material isencapsulated in an encapsulating polymer, which in some embodiments is athermoplastic polymer and in others is a thermosetting polymer.

In some exemplary embodiments of the invention, the particulatefluorescent particulate material is in the form of pigment particleshaving a size greater than about 2, 3, or 4 micrometers.

In some exemplary embodiments of the invention, the toner particle sizeis greater than about 3 or 5 micrometers. In some exemplary embodiments,the toner particle size is smaller than about 9 or 10 micrometers.

In exemplary embodiments of the invention, the particulate fluorescentmaterial comprises more than 40%, 50% or more of the non-volatile solidsportion of the particle.

In some embodiments, the toner polymer comprises an ethylene methacrylicacid copolymer.

In some embodiments of the invention, the method includes choosing theconditions of grinding and the toner polymer such that the tonerparticles are formed with fibrous extensions.

In some embodiments of the invention, mixing comprises:

-   -   first plasticizing the toner polymer with the carrier liquid;        and    -   subsequently adding additional carrier liquid and particulate        fluorescent material.

There is further provided, in accordance with some embodiments of theinvention, a printing method, comprising:

-   -   providing an electrostatic image;    -   developing the image with toner particles or a liquid toner        according to the invention or a toner produced in accordance        with the invention to form a visible image.

In exemplary embodiments of the invention, the method includestransferring the developed image to a final substrate. In someembodiments transferring the developed image to a final substratecomprises:

-   -   transferring the developed image to an intermediate transfer        member; and    -   subsequently transferring the developed image to the final        substrate.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Non-Limiting Examples of Toners

A first exemplary toner, in accordance with an embodiment of theinvention, can be prepared by:

(1) Loading 1400 grams of Nucrel 699 resin (an ethylene methacrylic acidcopolymer by Dupont), and 2600 grams of Isopar-L (an Isoparaffinichydrocarbon distributed by Exxon) in a Ross double planetary mixer type312-VI-031-089, preheated by a heating bath, set to 130° C. Theingredients are mixed for about ½ hour at speed control setting 2. Thespeed is increased to a speed setting of 3 for 60 minutes, then to aspeed setting of 6 for 1 hour. The heating is stopped and the mixer iscooled with a fan while mixing is continued at a speed setting of 4 for1.5 hours followed by mixing at a speed setting of 2 until thetemperature reaches 40° C. The result is a pasty material, having anon-volatile solids weight percentage of about 35%. The material isdiluted to a 23% solids content by the addition of a further quantity ofIsopar-L.

(2) 76.4 grams of the resulting 23% solids mixture, together with 0.43grams of aluminum streate and 105.17 grams of Isopar L, is loaded into aS0 ball mill (Union Process) with {fraction (3/16)}″ chrome steelgrinding media, together with 18 grams of pigment of one of the typesdescribed below. The speed is set near the maximum available.

The material is ground at 40° C. for 1 hour, followed by additionalgrinding at 30° C. for 19 hours. The result is discharged from the milland mixed with an amount of Isopar L to form a working dispersion at3.5% solids. The toner particles have fibrous extensions and a size ofbetween 5 micrometers and 9 micrometers as measured in a Coulter LS 200type particle size meter.

The toner is charged utilizing a charge director, for example, a chargedirector described in the above referenced U.S. Pat. No. 5,346,796 andcontaining 30 parts by weight lecithin, 30 parts by weight BBP and 6parts by weight G3300 as a stabilizer. The charge director, dissolved inIsopar-L is added in an amount of about 25-40 mg of solids of the chargedirector per gram of toner solids. A small amount of Marcol 82 may beadded to carrier liquid to form a mixed carrier liquid, as described inthe above references.

The following pigments have been successfully used as pigments forfluorescent pink toners. These are JST 17 (Radiant Color) pink toner,having a 2 micrometer size, Astral Pink A1 Seria FEX (Fiesta) having a 2micrometer size and Astral Pink A-1 Seria “A” (Fiesta) having a 4micrometer size. These resulted in a measured particles size of between6.85 and 7 micrometers. It is noted that the smaller pigment particlesgive a higher OD and reflection. Surprisingly, the grinding process doesnot appear to reduce the fluorescence, either because the integrity ofthe pigment is not destroyed or because size reduction of the pigment isnot effective to reduce the fluorescent effects.

These toners have a pink color. The toners described above have an OD ofbetween 0.28-0.90 and percentage reflectance of between 122 and 144 fordeveloped mass of between 0.1 and 0.2 mg of dry toner/cm², with thesmaller particles giving the higher values and JST 17 giving the highestvalues among the three types. These thicknesses are typical also of thethicknesses of toner achieved using standard ElectroInk on the samemachine.

The OD is measured using a standard X-Rite 408 densitometer (setting G),after: calibration utilizing the procedure described in the manual forthe device. The OD value is the amount of maximum reflection through anappropriate filter. The reflectance curve can be obtained using anX-Rite 968 or 938 spectrometer. The data generated includes reflectancevalues of the specimen at a range of 400-700 nm.

The result is a pink toner having a relatively high pigmentconcentration. It is noted that in order to achieve adequate imagebrightness, a very high pigment loading is desirable. In essence, thepigment loading for the above examples is about 50%. However, it isbelieved that, depending on the pigment used, 30-60% pigment loadingwill be optimum, although other values can be used as well.

For some colors of pigment, even these high pigment loadings of encaseddye pigments is not sufficient to provide high enough OD. In accordancewith another exemplary embodiment of the invention, two types ofpigments are used. The first of these is the encased dye pigment. Theother is second pigment which may be, for example an organic pigment,such as an aldezine pigment. The second pigment may be fluorescent, butis generally not an encased dye.

A second exemplary toner, in accordance with an embodiment of theinvention, can be prepared by performing the following after (1) fromthe previous example:

(2) 954 grams of the resulting 23% solids mixture, together with 108.1grams of Lumogen S0790 yellow pigment (aldazine yellow by BASF), 72.08grams JST-10 (yellow fluorescent encased pigment-Radiant Color), 14.41grams of JST 12 (fluorescent orange) and 1151.4 grams of Isopar L, isloaded into a S1 ball mill (Union Process) with {fraction (3/16)}″chrome steel grinding media. The Lumogen pigment is fluorescent.

The material is ground at 58° C. for 1 hour, followed by additionalgrinding at 40° C. for 19 hours at 250 RPM. The result is dischargedfrom the mill and mixed with an amount of Isopar L to form a workingdispersion at 3.5% solids. The toner particles have fibrous extensionsand a size of about 7 micrometers as measured in a Coulter LS 200 typeparticle size meter.

The toner is charged utilizing a charge director, for example, a chargedirector described in the above referenced U.S. Pat. No. 5,346,796 andcontaining 30 parts by weight lecithin, 30 parts by weight BBP and 6parts by weight G3300 as a stabilizer. The charge director, dissolved inIsopar-L is added in an amount of about 10-30 mg of solids of the chargedirector per gram of toner solids. A small amount of Marcol 82 may beadded to carrier liquid to form a mixed carrier liquid, as described inthe above references.

This toner has a yellow color with an orange hue. The total pigmentloading by weight of solids is 47%, with 44.4% of the total pigment(20.9% of total solids) being of the encased dye type.

For a yellow toner with a green hue the following procedure is followed:

(2) 1044 grams of the resulting mixture, together with 110.75 grams ofLurnogen S0790 yellow pigment (aldazine yellow by BASF), 42.44 gramsJST-10, 20.7 grams of JST 31 (fluorescent green) and 1082.11 grams ofIsopar L, is loaded into a S1 ball mill (Union Process) with {fraction(3/16)}″ chrome steel grinding media.

The material is ground at 40° C. for 20 hours. The result is dischargedfrom the mill and mixed with an amount of Isopar L to form a workingdispersion at 2% solids. The toner particles have fibrous extensions anda size of about 8.6 micrometers as measured in a Coulter LS 200 typeparticle size meter.

Charging and dilution of the result is carried out as above.

The total pigment loading by weight of solids is 42%, with 36.3% of thetotal pigment (15.3% of the total solids) being of the encased dye type.

Of course, a yellow toner in which the fluorescent color was also yellowcould have been made by the same method by deleting the orange or greenfluorescent pigment and increasing the amount of JST-10 pigment.

It should be understood that the above examples are experimental tonersthat were; produced on an experimental basis. Neither the process northe colors were optimized. Variations on the measured values may beexpected between batches. Other ratios of pigments and various pigmentcolors may be used to achieve different colors and effects. In addition,pigments of different types may be used, such as the PC series (3micrometers thermoplastic polymer encapsulation) and PC series (3micrometers thermosetting polymer encapsulation) of Radiant Color.Other, larger or smaller pigments may be used.

It will be further understood that many variations of the tonersaccording to the: invention are possible and the toners that are definedby the claims may be produced using a wide variety of polymers. Inparticular, other ethylene methacrylic acid copolymers and ionomers andesters of ethylene methacrylic acid copolymers of various molecularweights may be used in place of Nucrel 966. In some preferredembodiments of the invention low molecular weight ethylene acrylic acidcopolymers and/or their ionomers and esters and/high molecular weightethylene polymers with high acid functionality sold under the trade nameof ELVAX, by Dupont may be substituted for the resin indicated above.Other charge directors, as known in the art may also be used.

The toner is useful for printing utilizing substantially conventionalsystems as described in the above referenced patents and applications,in which various electrostatic images are sequentially formed on aphotoreceptor. A same conventional roller developer is used fordeveloping all of the separations by introduction of a low tonerparticle concentration liquid toner (such as 3.5%) in the space betweenthe developer roller and the photoreceptor. Such systems include theabove referenced E-Print 1000®, Ominius®, Turbostream™ and Cardpress™.

It is also believed to be useful in printers of the type described inPCT published applications WO 93/01531 and WO 95/10801 and PCTapplication PCT/IL98/00553.

While the above referenced printers utilize an intermediate transfermember, the invention is also useful in printers in which the toner istransferred directly from an imaging plate (such as a photoreceptor) toa final substrate.

While a number of different embodiments have been shown, details of oneembodiment of the invention may, where applicable, in other embodiments.Similarly, some details shown in the embodiments, while preferred, arenot essential and some preferred embodiments of the invention may omitthem.

As used herein, the terms “have”, “include” and “comprise” or theirconjugates, as used herein mean “including but not limited to”.

1. Charged toner particles for use in electrostatic imaging, comprising:a toner polymer; and at least one particulate fluorescent material,wherein the toner particles are formed with fibrous extensions.
 2. Aliquid toner, comprising: a carrier liquid; and charged toner particlesdispersed in the carrier liquid, said charged particles comprising: atoner polymer; and at least one particulate fluorescent material,wherein the toner particles are formed with fibrous extensions.
 3. Aliquid toner according to claim 2 wherein the carrier liquid issubstantially non-conducting.
 4. A liquid toner according to claim 2,including a charge director for aiding in the charging of the tonerparticles.
 5. A printing method, comprising: providing an electrostaticimage; developing the image with a toner according to claim
 2. 6. Amethod according to claim 5 and including: transferring the developedimage to a final substrate.
 7. A method according to claim 6 whereintransferring the developed image to a final substrate comprises:transferring the developed image to an intermediate transfer member; andsubsequently transferring the developed image to the final substrate. 8.A liquid toner according to claim 2 wherein the charged toner particlescomprise a pigment additional to the at least one particulatefluorescent material.
 9. A liquid toner according to claim 8 wherein theadditional pigment is fluorescent.
 10. A liquid toner according to claim8 wherein the additional pigment is not fluorescent.
 11. A liquid toneraccording to claim 8 wherein the fluorescent color of the at least oneparticulate fluorescent material is different from that of theadditional pigment.
 12. A liquid toner according to claim 8 wherein theat least one particulate fluorescent material and the additional pigmentis greater than about 30% by weight of the total dry solids of the tonerparticle.
 13. A liquid toner according to claim 8 wherein the at leastone particulate fluorescent material and the additional pigment isgreater than about 40% by weight of the total dry solids of the tonerparticle.
 14. A liquid toner according to claim 2 wherein theparticulate fluorescent material comprises an encapsulated dye material.15. A liquid toner according to claim 14 wherein the dye material isencapsulated in an encapsulating polymer.
 16. A liquid toner accordingto claim 15 wherein the encapsulating polymer is a thermoplasticpolymer.
 17. A liquid toner according to claim 15 wherein theencapsulating polymer is a thermosetting polymer.
 18. A liquid toneraccording to claim 2 wherein the particulate fluorescent particulatematerial is in the form of pigment particles having a size greater thanabout 2 micrometers.
 19. A liquid toner according to claim 2 wherein theparticulate fluorescent particulate material is in the form of pigmentparticles having a size greater than about 3 micrometers.
 20. A liquidtoner according to claim 2 wherein the particulate fluorescentparticulate material is in the form of pigment particles having a sizeof 4 micrometers or more.
 21. A liquid toner according to claim 2wherein the toner particle size is greater than about 3 micrometer. 22.A liquid toner according to claim 2 wherein the toner particle size isgreater than about 5 micrometers.
 23. A liquid toner according to claim2 wherein the toner particle size is smaller than about 10 micrometers.24. A liquid toner according to claim 2 wherein the toner particle sizeis smaller than about 9 micrometers.
 25. A liquid toner according toclaim 2 wherein the particulate fluorescent material comprises more than40% of the non-volatile solids portion of the particle.
 26. A liquidtoner according to claim 25 wherein the particulate fluorescent materialcomprises more than 50% of the non-volatile solids portion of theparticle.
 27. A liquid toner according to claim 2 wherein the tonerpolymer comprises an ethylene methacrylic acid copolymer.
 28. A methodof producing a liquid toner comprising: mixing a toner polymer, acarrier liquid and particulate fluorescent material; and grinding themixture until toner particles are produced, including choosing theconditions of grinding and the toner polymer such that the tonerparticles are formed with fiberous extensions.
 29. A method according toclaim 28 wherein mixing comprises mixing a pigment additional to the atleast one particulate fluorescent material with the other materials. 30.A method according to claim 29 wherein the additional pigment isfluorescent.
 31. A method according to claim 29 wherein the additionalpigment is not fluorescent.
 32. A method according to claim 29 whereinthe fluorescent color of the at least one particulate fluorescentmaterial is different from that of the additional pigment.
 33. A methodaccording to claim 29 wherein the at least one particulate fluorescentmaterial and the additional pigment is greater than about 30% by weightof the total dry solids of the mixture.
 34. A method according to claim33 wherein the at least one particulate fluorescent material and theadditional pigment is greater than about 45% by weight of the total drysolids of the toner particle.
 35. A method according to claim 28 whereinthe particulate fluorescent material comprises an encapsulated dyematerial.
 36. A method according to claim 35 wherein the dye material isencapsulated in an encapsulating polymer.
 37. A method according toclaim 36 wherein the encapsulating polymer is a thermoplastic polymer.38. A method according to claim 36 wherein the encapsulating polymer isa thermosetting polymer.
 39. A method according to claim 28 wherein theparticulate fluorescent particulate material is in the form of pigmentparticles having a size greater than about 2 micrometers.
 40. A methodaccording to claim 28 wherein the grinding is continued until the tonerparticle size is smaller than about 10 micrometers.
 41. A methodaccording to claim 28 wherein the grinding is interrupted while theparticle size is greater than about 3 micrometers.
 42. A methodaccording to claim 28 wherein the grinding is interrupted while theparticle size is greater than about 5 micrometers.
 43. A methodaccording to claim 28 wherein the particulate fluorescent particulatematerial is in the form of pigment particles having a size greater thanabout 3 micrometers.
 44. A method according to claim 28 wherein thetoner particle size is smaller than about 5 micrometer.
 45. A methodaccording to claim 28 wherein the particulate fluorescent materialcomprises more than 40% of the non-volatile solids portion of themixture.
 46. A method according to claim 45 wherein the particulatefluorescent material comprises more than 50% of the non-volatile solidsportion of the mixture.
 47. A method according to claim 28 wherein thetoner polymer comprises an ethylene methacrylic acid copolymer.
 48. Amethod according to claim 28 wherein mixing comprises: firstplasticizing the toner polymer with the carrier liquid; and subsequentlyadding additional carrier liquid and particulate fluorescent material.